package cn.shenzhenlizuosystemapp.Common.Base;

import android.os.NetworkOnMainThreadException;

import java.net.InetAddress;
import java.net.UnknownHostException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Random;

/**
 * 调用方法 String guid = new CreateGuid().toString();
 */
public class CreateGuid

{
    /**
     * The value before MD5
     */
    private String valueBeforeMD5 = "";

    /**
     * The value after MD5
     */
    private String valueAfterMD5 = "";

    /**
     * The Random object to generate random number.
     */
    private static Random myRand = null;

    /**
     * To generate random number with security.
     */
    private static SecureRandom mySecureRand = null;

    /**
     * The id of localhost.
     */
    private static String s_id = "";

    /**
     * The flag.
     */
    private static final int PAD_BELOW = 0x10;

    /**
     * The flag.
     */
    private static final int TWO_BYTES = 0xFF;

    /**
     * Static block to take care of one time secureRandom seed. It takes a few
     * seconds to initialize SecureRandom. You might want to consider removing
     * this static block or replacing it with a "time since first loaded" seed
     * to reduce this time. This block will run only once per JVM instance.
     */
    static
    {
        mySecureRand = new SecureRandom();
        long secureInitializer = mySecureRand.nextLong();
        myRand = new Random(secureInitializer);

        try
        {
            InetAddress address = InetAddress.getLocalHost();
            if (null != address)
            {
                s_id = address.toString();
            }
        }
        catch (UnknownHostException e)
        {
            e.printStackTrace();
        }
        catch (NetworkOnMainThreadException e)
        {
            e.printStackTrace();
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }

    /**
     * Default constructor. With no specification of security option, this
     * constructor defaults to lower security, high performance.
     */
    public CreateGuid()
    {
        getRandomGUID(false);
    }

    /**
     * Constructor with security option. Setting secure true enables each random
     * number generated to be cryptographically strong. Secure false defaults to
     * the standard Random function seeded with a single cryptographically
     * strong random number.
     */
    public CreateGuid(boolean secure)
    {
        getRandomGUID(secure);
    }

    /**
     * Method to generate the random GUID
     */
    public void getRandomGUID(boolean secure)
    {
        MessageDigest md5 = null;
        StringBuffer sbValueBeforeMD5 = new StringBuffer(128);

        try
        {
            md5 = MessageDigest.getInstance("MD5");
        }
        catch (NoSuchAlgorithmException e)
        {
            e.printStackTrace();
        }

        try
        {
            long time = System.currentTimeMillis();
            long rand = secure ? mySecureRand.nextLong() : myRand.nextLong();

            sbValueBeforeMD5.append(s_id);
            sbValueBeforeMD5.append(":");
            sbValueBeforeMD5.append(Long.toString(time));
            sbValueBeforeMD5.append(":");
            sbValueBeforeMD5.append(Long.toString(rand));

            valueBeforeMD5 = sbValueBeforeMD5.toString();
            md5.update(valueBeforeMD5.getBytes());

            byte[] array = md5.digest();
            StringBuffer sb = new StringBuffer(32);
            for (int j = 0; j < array.length; ++j)
            {
                int b = array[j] & TWO_BYTES;
                if (b < PAD_BELOW)
                {
                    sb.append('0');
                }

                sb.append(Integer.toHexString(b));
            }

            valueAfterMD5 = sb.toString();

        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }

    /**
     * Convert to the standard format for GUID (Useful for SQL Server
     * UniqueIdentifiers, etc. Example: C2FEEEAC-CFCD-11D1-8B05-00600806D9B6
     */
    @Override
    public String toString()
    {
        String raw = valueAfterMD5.toUpperCase();

        StringBuffer sb = new StringBuffer(64);
        sb.append(raw.substring(0, 8));
        sb.append("-");
        sb.append(raw.substring(8, 12));
        sb.append("-");
        sb.append(raw.substring(12, 16));
        sb.append("-");
        sb.append(raw.substring(16, 20));
        sb.append("-");
        sb.append(raw.substring(20));

        return sb.toString();
    }
}

